1. Field of the Disclosure
The present invention relates generally to power supplies, and in particular but not exclusively, relates to switching devices for the switched mode power supplies.
2. Background
A wide variety of household or industrial appliances require a regulated direct current (dc) power source for their operation. Switch mode power supplies are to convert a low frequency (e.g. 50 Hz or 60 Hz) high voltage alternating current (ac) or a direct current (dc) input voltage to the required level of dc output voltage. Various types of switch mode power supplies are popular because of their well-regulated output, high efficiency, and small size along with the safety and protection features. Flyback converters, forward converters, various configurations of resonance converters are among the very popular example topologies that are utilized for switch mode power supplies.
One major component of a switch mode power supply is the high frequency (HF) switching device that chops the dc, rectified or low frequency ac input to HF pulses by utilizing a controller to turn on and off the switching device. Different control methods such as pulse width modulation (PWM), pulse frequency modulation (PFM), or on-off control, which disables some of the cycles of the switching waveform generated by the controller, are utilized to regulate the output voltage with respect to load and line variations.
The HF pulses at the output of the power supply are rectified and filtered to provide a regulated dc output, which may then be provided to the electronic device being powered. The HF pulses are transferred to the output through a HF transformer, which is typically small and utilized to change the input voltage level to an output voltage level as well as provide galvanic isolation between the input of the power supply and the electronic device being powered at output of the power supply. The switching device in different configurations may appear as a single switching device or a switching circuit module that includes a combination of multiple switching devices. The different configurations employed in the different topologies may include a single switching action or synchronized multiple switching actions in half-bridge or full-bridge switching configurations.
Output regulation in a switched mode power supply is usually provided by sensing the output of the power supply and controlling the power supply in a closed loop. The output sense and feedback or control signal can be provided with an opto-coupler from a sense circuit coupled to the output. In some other switched mode power supplies, the feedback or control signal could be extracted indirectly from an extra winding that is magnetically coupled to the output winding of the power supply on the same transformer core called a bias, auxiliary or feedback winding, which in some cases may also provide the supply for the controller.
Corresponding reference characters indicate corresponding components throughout the several views of the drawings. Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention.